<template>
  <div class="app-container">

    <el-row :gutter="24">

      <el-col :span="24" style="margin-bottom: 20px">

        <el-alert
          title="点击`开始考试`后将自动进入考试，请诚信考试！"
          type="error"
          style="margin-bottom: 10px"
        />

        <el-card class="pre-exam">

          <div><strong>考试名称：</strong>{{ detailData.title }}</div>
          <div><strong>考试时长：</strong>{{ detailData.totalTime }}分钟</div>
          <div><strong>试卷总分：</strong>{{ detailData.totalScore }}分</div>
          <div><strong>及格分数：</strong>{{ detailData.qualifyScore }}分</div>
          <div><strong>考试描述：</strong>{{ detailData.content }}</div>
          <div><strong>开放类型：</strong> {{ detailData.openType | examOpenType }}</div>
          <div><strong style="color: red">开始考试前，请先点击检测摄像头！</strong></div>
        </el-card>

      </el-col>

      <el-col :span="24">

        <el-button :loading="loading" :disabled="disabled" type="primary" icon="el-icon-caret-right" @click="handleCreate">
          开始考试
        </el-button>

        <el-button @click="handleBack">
          返回
        </el-button>

        <el-button @click="getCompetence()">检测摄像头</el-button>
        <!--      <el-button @click="stopNavigator()">关闭摄像头</el-button>-->
        <!--      <el-button @click="setImage()">拍照</el-button>-->
      </el-col>

    </el-row>
    <div class="camera_outer">
      <video id="videoCamera" :width="videoWidth" :height="videoHeight" autoplay :style="margin" />
      <canvas id="canvasCamera" style="display:none;" :width="videoWidth" :height="videoHeight" />
      <div v-if="imgSrc" class="img_bg_camera">
        <img :src="imgSrc" alt="" class="tx_img">
      </div>
    </div>
  </div>

</template>

<script>
import { fetchDetail } from '@/api/exam/exam'
import { createPaper } from '@/api/paper/exam'

export default {
  data() {
    return {
      detailData: {},
      postForm: {
        examId: '',
        password: ''
      },
      rules: {
        password: [
          { required: true, message: '考试密码不能为空！' }
        ]
      },

      loading: false,
      disabled: true,

      // 摄像头相关
      videoWidth: navigator.userAgent.indexOf('Firefox') > -1 ? 600 : 400,
      videoHeight: 300,
      margin: navigator.userAgent.indexOf('Firefox') > -1 ? 'margin-left: -100px' : '',
      imgSrc: '',
      thisCancas: null,
      thisContext: null,
      thisVideo: null
    }
  },

  created() {
    this.postForm.examId = this.$route.params.examId
    this.fetchData()
  },

  methods: {

    fetchData() {
      fetchDetail(this.postForm.examId).then(response => {
        this.detailData = response.data
      })
    },

    handleCreate() {
      const that = this
      this.loading = true

      createPaper(this.postForm).then(response => {
        console.log(response)

        if (response.code === 0) {
          setTimeout(function() {
            this.loading = false
            that.dialogVisible = false
            that.$router.push({ name: 'StartExam', params: { id: response.data.id }})
          }, 1000)
        }
      }).catch(() => {
        this.loading = false
      })
    },

    handleBack() {
      this.$router.push({ name: 'ExamOnline' })
    },

    getCompetence() {
      var _this = this
      this.thisCancas = document.getElementById('canvasCamera')
      this.thisContext = this.thisCancas.getContext('2d')
      this.thisVideo = document.getElementById('videoCamera')
      // 旧版本浏览器可能根本不支持mediaDevices，我们首先设置一个空对象
      if (navigator.mediaDevices === undefined) {
        navigator.mediaDevices = {}
      }
      // 一些浏览器实现了部分mediaDevices，我们不能只分配一个对象
      // 使用getUserMedia，因为它会覆盖现有的属性。
      // 这里，如果缺少getUserMedia属性，就添加它。
      if (navigator.mediaDevices.getUserMedia === undefined) {
        navigator.mediaDevices.getUserMedia = function(constraints) {
          // 首先获取现存的getUserMedia(如果存在)
          var getUserMedia = navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.getUserMedia
          // 有些浏览器不支持，会返回错误信息
          // 保持接口一致
          if (!getUserMedia) {
            return Promise.reject(new Error('getUserMedia is not implemented in this browser'))
          }
          // 否则，使用Promise将调用包装到旧的navigator.getUserMedia
          return new Promise(function(resolve, reject) {
            getUserMedia.call(navigator, constraints, resolve, reject)
          })
        }
      }
      var constraints = { audio: false, video: { width: this.videoWidth, height: this.videoHeight, transform: 'scaleX(-1)' }}
      navigator.mediaDevices.getUserMedia(constraints).then(function(stream) {
        // 旧的浏览器可能没有srcObject
        if ('srcObject' in _this.thisVideo) {
          _this.thisVideo.srcObject = stream
        } else {
          // 避免在新的浏览器中使用它，因为它正在被弃用。
          _this.thisVideo.src = window.URL.createObjectURL(stream)
        }
        _this.thisVideo.onloadedmetadata = function(e) {
          _this.thisVideo.play()
          _this.disabled = false
          _this.$message({
            showClose: true,
            message: '摄像头检测成功。',
            type: 'success'
          })
        }
      }).catch(err => {
        console.log(err)
        _this.$alert('摄像头开启失败，请检查摄像头是否可用！', '错误', {
          type: 'error',
          confirmButtonText: '确定',
          callback: action => {
          }
        })
      })
    },
    //  绘制图片（拍照功能）
    setImage() {
      var _this = this
      // 点击，canvas画图
      _this.thisContext.drawImage(_this.thisVideo, 0, 0, _this.videoWidth, _this.videoHeight)
      // 获取图片base64链接
      var image = this.thisCancas.toDataURL('image/png')
      _this.imgSrc = image
      this.$emit('refreshDataList', this.imgSrc)
    },
    // base64转文件
    dataURLtoFile(dataurl, filename) {
      var arr = dataurl.split(',')
      var mime = arr[0].match(/:(.*?);/)[1]
      var bstr = atob(arr[1])
      var n = bstr.length
      var u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new File([u8arr], filename, { type: mime })
    },
    // 关闭摄像头
    stopNavigator() {
      this.thisVideo.srcObject.getTracks()[0].stop()
    }

  }
}
</script>

<style scoped>

  .pre-exam div {

    line-height: 42px;
    color: #555555;
  }

</style>

